This invention relates to an apparatus for automatically maintaining tension in extendable flexible tarp cover systems such as systems used on flatbed vehicles.
Flatbed trailers are used to haul a variety of goods ranging from large heavy articles, such as machinery, to palletized goods. It is desirable, particularly with regard to weather sensitive goods, to provide a cover to protect the load during transit. Various types of cover systems have been used, ranging from simple tarps held in place with cargo straps and tie downs, to retractable tarp systems that cover and protect the entire trailer bed from weather and debris.
One such retractable tarp system is the Conestoga(copyright) tarp cover system manufactured and sold by Aero Industries of Indianapolis, Ind. Details of this type of cover system are disclosed in the U.S. Pat. No. 4,711,484, issued on Dec. 8, 1987, U.S. Pat. No. 4,902,064, issued on Feb. 20, 1990, and U.S. Pat. No. 5,538,313, issued on Jul. 23, 1996, all of which are owned by the assignee of the present invention. The Conestoga(copyright) tarp system was developed to provide a tarp cover system that not only effectively encloses the cargo area but also protects or seals the tarp cover deployment system. The Conestoga(copyright) system includes a wheel and track deployment system that rides along the outside edges of the trailer. In this manner, the entire trailer bed is under cover.
With flexible cover systems like the Conestoga(copyright), it is important to keep the tarp cover in tension. The tensioned tarp more effectively seals the cargo area from the elements, and resists flapping due to wind and road vibration. In the typical extendable tarp system, the tarp cover is stretched slightly on deployment and latched to a rear bulkhead element.
However, the tarp cover stretches and becomes loose over time. This leads to billowing and flapping of the cover, particularly at the end sections, which accelerates wear and deterioration of the tarp cover if not addressed. The ""064 patent addresses this problem somewhat in the design of the tarp bow guide tracks. The rear portion of each guide track is inclined downwardly, so that as the rearmost bow carrier enters this part of the track, the bow which is attached to this carrier xe2x80x9cleansxe2x80x9d back and away from the front of the trailer, thereby pulling the tarp taught. Although this approach is automatic in that no special action by the driver of the vehicle is necessary, the amount of tightening that it provides is limited. Moreover, the degree of tightening is relatively fixed and uniform around the entire perimeter of the tarp cover.
Accordingly, a need remains for an extendable flexible cover system that can compensate for stretching of the tarp cover that occurs in use and that can maintain proper tensioning across the tarp during normal use and for the life of the tarp cover.
The present invention provides a self-tensioning tarp cover system. The invention is particularly suited for a hauling vehicle such as a flatbed truck, but can be used in other applications to define an enclosed cargo or storage area. In one embodiment of the invention, the system includes a tarp cover segment connected at one end to an extension mechanism and having an opposite end connectable to an adjusting element, which is movable relative to the extension mechanism to tighten the cover. A biasing mechanism is disposed between the extension mechanism and the adjusting element to bias the adjusting element in a direction to tighten the tarp cover.
In a preferred embodiment, the biasing mechanism includes a number of springs under compression disposed between the extension mechanism and the adjusting element along with a limiting element at each spring location that limits the extension of the spring. Most preferably, the limiting element includes a nut and bolt assembly, coaxial with the spring and adjustable for setting a maximum spring extension.
The present invention accomplishes one objective of providing a cover system that applies tension to a flexible tarp cover to prevent billowing and flapping of the cover to maximize the useful life of the cover. It is another object to provide a cover system that automatically applies tension to the tarp cover when the tarp cover system is deployed. The invention accomplishes a further object of maintaining proper tensioning across the tarp cover. Yet another object of the invention is to provide a cover system that can vary the amount of tension applied around the perimeter of a tarp cover system. These and other objects, advantages, and benefits are accomplished according to the devices of the following descriptions of the preferred embodiments of the present invention.